The manufacture of pharmaceuticals by blending several powders in production quantities requires careful control to ensure uniformity within a given batch and from one batch to another. A typical pharmaceutical may involve five or more ingredients in powder form. Often there is only a single active ingredient that comprises a very small fraction of the total amount of the ingredients to be combined, typically measured in micrograms or milligrams. Unless the mixing is thorough, parts of the production batch will have an insufficient amount of active ingredient to be effective, and parts of the production batch will have an excess amount of active ingredient and be potentially detrimental. In most cases, when the blending is complete the powder is either compressed into tablets or filled into capsules to provide measured dose quantities. If the blending is not thorough, the measured dose quantities will not be equal.
Blending of powders is commonly done in a tumbler, a closed container that is caused to rotate, typically end over end, to mix the multiple powder ingredients to form a homogeneous blend. Many tumbling blenders include an intensifier bar that is rotated at high speed within the blender. A known type blender that effectively mixes powders is known as a V-blender or a double cone blender. The thoroughness of the mixing depends on the characteristics of the individual ingredients and the length of time the tumbler is operated. Using a tumbling blender, such as a V-blender with an intensifier bar, yields a more uniform blend than a stationary blender, such as a ribbon blender. However, even blending of a micronized active ingredient with other ingredients in a tumbling blender with an intensifier bar does not always yield a uniform blend. In some situations, a micronized active ingredient will develop a static charge and form small aggregates which do not break up during the blending process, even with an intensifier bar. To correct the problem of aggregated powder, the powder batch may be first blended, then removed from the blender and sifted or milled, and then re-loaded into the blender to be blended again. This multiple handling process is time consuming and generates dust from the powder ingredients.
An improvement on the basic tumbler is taught in U.S. Pat. No. 7,056,010 to Davies for a Blender For Mixing Particulate Solid Materials Including An Internal Baffle. While the Davies blender appears to improve the effectiveness of blending multiple powders, the requirement for breaking down powder clumps still exists.
Certain powders are blended with an included ingredient specifically intended for coating particles of other powders, for example a lubricating powder. The degree of adhesion of a coating ingredient to a powder particle may be improved by the application of pressure, rather than simply allowing the components to randomly contact one another.